The present invention pertains to naphthalocyanine dimer compounds, and their use in optical recording media. More particularly, the present invention relates to naphthalocyanine oxo-bridged dimer compounds represented by the general formula: EQU RO--YNc--O--NcY--OR (I)
and the use of such compounds in the information layer of an optical information recording medium. The present invention also relates to a novel process for the preparation of such naphthalocyanine oxo-bridged dimer compounds.
The recording medium, of course, is one of the key elements in any optical information storage system. The commercial viability of the recording medium depends upon such technical parameters as the sharpness in recording and playback of the information, i.e., a high signal to noise ratio. Dyes and pigments have accordingly been employed in information layers of recording media, often to enhance the sensitivity of the recording layers at the particular wavelength of the laser being used, which results in a much sharper recording and playback of information.
For example, U.S. Pat. No. 4,492,750 discloses an infrared sensitive optical recording composition containing as a component thereof a dispersion of a resinous binder and a soluble naphthalocyanine substituted on its aromatic rings with hydrogen or alkyl groups containing from 4 to about 8 carbon atoms. The central group of the naphthalocyanine compound is two hydrogen atoms, a divalent, trivalent, or tetravalent metal complex.
U.S. Pat. No. 4,622,179 discloses a naphthalocyanine compound wherein straight chain or branched chain alkyl groups of 5 to 12 carbon atoms are substituted on its aromatic rings with a metal such as Cu, Ni, Mg, Pb, Pd, V, Co, Nb, Al, Sn, In, Fe, and Ge, or its oxide, chloride or bromide, forming the central group of the naphthalocyanine compound. The use of the naphthalocyanine compound as a dyestuff in optical disks is also disclosed.
U.S. Pat. No. 4,719,613 discloses a naphthalocyanine compound wherein an oxygen attached to straight chain or branched chain alkyl groups of 4 to 12 carbon atoms are substituted on its aromatic rings with a metal, metal oxide or metal halide forming the central group of the naphthalocyanine compound. The use of the naphthalocyanine compound as a dyestuff in optical disks is also disclosed.
U.S. Pat. No. 4,725,525 discloses a naphthalocyanine chromophore compound, e.g., a sulfonamidonaphthalocyanine having silicon or germanium as the central hetero atom, used as an information layer of the recording medium.
Lee Arnold Schechtman in his thesis Compounds, Poly(metallonaphthalocyanines) and Related Macrocyclic Compounds, August, 1983, Dept. of Chemistry, Case Western Reserve University, discloses a particular chromophore which absorbs light at the wavelength of about 770 nm, i.e., bis-tri-n-hexylsiloxysilicon naphthalocyanine. The suitability of such a chromophore for use in an optical recording medium, however, has heretofore not been suggested or explored.
While dyes or pigments have been employed in information storage layers of optical recording media due to their excellent absorption properties, the search for an improved dye or pigment exhibiting stability and intense absorption, as well as commercial viability due to its ease of preparation and reproducibility in said preparation synthesis, is continuously ongoing.
Accordingly, it is an object of the present invention to provide naphthalocyanine compounds which can be prepared directly and easily, without the need for extreme precautions.
It is also an object of the present invention to provide dimer naphthalocyanine compounds exhibiting good stability and a usefulness in optical information storage media.
In another object of the present invention, a process for preparing such a dimer naphthalocyanine compound efficiently and inexpensively is provided, whereby the process uses a naphthalocyanine dihalide precursor.
Still another object of the present invention is to provide a novel process for efficiently and effectively, as well as reproducibly, preparing a naphthalocyanine compound which is extremely useful in optical recording media applications, which compound absorbs at a wavelength of about 780 nm.
These and other objects, as well as the scope, nature and utilization of the invention, will be apparent to those skilled in the art from the following description and the appended claims.